Microwave signals with many kinds of modulation formats, such as various forms of CDMA signals, have high but arbitrary peak to average ratios over a very wide dynamic range. These signals pose serious challenges to accurate and rapid power level measurements over wide dynamic ranges.
Some methods have been described that attempt to place the power sensing path in the "square law" region (see U.S. Pat. No. 4,943,764) or otherwise improve power sensor performance (see U.S. Pat. No. 5,204,613). However, the accuracy afforded measurement of modulated signals with high peak to average ratios is not satisfactory.
Another technique which attempts to accurately perform wide dynamic range microwave power measurements for modulations with high peak-to-average ratios involves characterizing a continuous wave (CW) sensor for a given kind of modulation over the power range of interest, for example -70 dBm to +20 dBm. This technique has the drawback of being accurate only to the extent that the modulation being measured is fairly similar to the modulation form for which the sensor was originally charaterized. Because commercial formats such as CDMA are changing rapidly, a sensor characterized for one form of modulation risks obsolescence.
No currently known methods are entirely satisfactory from an accuracy or application standpoint. What is needed is a power measurement device that makes measurements of signals over a 90 dB dynamic range (about -70 dBm to about +20 dBm) with improved accuracy in measuring high peak average power ratio signals above -20 dB.